Full Name: 
Sodar-RASS Metek DSDPA.90-24
Short Name: 
HAIS Instrument: 

Manufacturer or Builder:

Date Acquired: 
January, 2004
Lead Contact: 
William Brown
Measurements Provided: 
Wind and virtural temperature profiles from near the surface up into the lower boundary layer
Typical Sampling Rates: 
10 minutes
General Description: 













The Atmospheric Profiling Group in ISF operates a mini-Doppler Sodar-RASS as part of the Integrated Sounding System (ISS).

SODAR = SOnic Detection And Ranging

RASS = Radio Acoustic Sounding System

The Sodar transmits acoustic pulses (literally beeps) upwards and as these are reflected back down to the sodar they are Doppler shifted by the wind.  It measures the Doppler shift  of the reflected pulses in multiple beam directions and uses that information to calculate the 3-dimensional wind above the sodar.  A low power radar is sometimes deployed with the Sodar to enable RASS measurements of virtual temperature.  The radar can detect the acoustic pulses as they propagate upwards, and since the speed of sound is related to temperature, the system can determine the approximate virtual temperature aloft.

The ISS sodar is a Metek DSDPA.90-24 sodar and is equipped with a RASS add-on.  This is a smaller version of the DSDPA.90-64 described in Engelbart, et al (1999).  The RASS radar is a vertically pointing 915 MHz 20W CW radar.


Engelbart. D., H. Steinhagen, U. Gorsdorf, J. Neisser, H-J. Kirtzel, and G. Peters : "First Results of Measurements with a Newly Designed Phase-Array SODAR with RASS", Meteorol. Atmos. Phys., 71, p. 61-68, 1999.

Measurement Characteristics: 

The Sodar-RASS produces wind and virtual temperature profiles.   The maximum height of reliable measurement depends on many factors such as background noise, atmospheric conditions, and even the wind speed.  Typically wind measurements are made at 20 meter steps from about 50 meters above ground up to the 200 to 400 meter range.  Virtual temperature measurements are typically available up to the 120 to 200 meter range.  Measurements are usually made with 10 minute averages, although raw reflectivity and vertal wind samples are available every 10 to 20 seconds. The system also can estimate turbulence.

Calibration Methods: 

Comparisons with towers, radiosondes and radar wind profilers indicate that the system is accurate to approximately 1 m/s in winds and 1C in virtual temperature, although performance varies depending on atmospheric conditions.

History of Significant Changes: 

The Metek sodar (without RASS) was purchased in late 2001.  The RASS extension was added in mid-2005.   The system was upgraded with a new computer and other components in 2010/2011.